// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "media/audio/scoped_task_runner_observer.h"

#include "base/bind.h"
#include "base/synchronization/waitable_event.h"

namespace media {

ScopedTaskRunnerObserver::ScopedTaskRunnerObserver(
    const scoped_refptr<base::SingleThreadTaskRunner>& task_runner)
    : task_runner_(task_runner)
{
    ObserveLoopDestruction(true, NULL);
}

ScopedTaskRunnerObserver::~ScopedTaskRunnerObserver()
{
    ObserveLoopDestruction(false, NULL);
}

void ScopedTaskRunnerObserver::ObserveLoopDestruction(
    bool enable,
    base::WaitableEvent* done)
{
    // Note: |done| may be NULL.
    if (task_runner_->BelongsToCurrentThread()) {
        base::MessageLoop* loop = base::MessageLoop::current();
        if (enable) {
            loop->AddDestructionObserver(this);
        } else {
            loop->RemoveDestructionObserver(this);
        }
    } else {
        base::WaitableEvent event(base::WaitableEvent::ResetPolicy::AUTOMATIC,
            base::WaitableEvent::InitialState::NOT_SIGNALED);
        if (task_runner_->PostTask(FROM_HERE,
                base::Bind(&ScopedTaskRunnerObserver::ObserveLoopDestruction,
                    base::Unretained(this), enable, &event))) {
            event.Wait();
        } else {
            // The message loop's thread has already terminated, so no need to wait.
        }
    }

    if (done)
        done->Signal();
}

} // namespace media.
